Objective: To assess the prevalence of overweight, obesity and underweight among Vietnamese adults living in urban areas of Ho Chi Minh City (HCMC), Vietnam. Design: This cross-sectional survey was conducted in the local health stations of 30 randomly selected wards, which represent all 13 urban districts of HCMC, over a period of 2 months from March to April 2004. Subjects: A total of 1488 participants aged 20-60 years completed the interview, physical examination and venous blood collection. Measurements: Anthropometric measurements of body weight, height, waist and hip circumference were taken to construct indicators of adiposity including body mass index (BMI), waist circumference, and waist-to-height and waist-to-hip ratios. Both systolic and diastolic blood pressure and biochemical indicators of cardiovascular disease and type II diabetes risk (lipid profile and fasting blood glucose) were also measured. Results: The age and sex standardized prevalence of overweight and obesity using Asian specific BMI cutoffs of 23.0 and 27.5 kg/m2 was 26.2 and 6.4%, respectively. The prevalence of overweight and obesity was slightly higher in females (33.6%) than males (31.6%), and progressively increased with age. The age and sex-standardized prevalence of underweight (BMI <18.5 kg/m2) among Vietnamese adults living in HCMC was 20.4%. The prevalence was slightly higher in males (22.0%) than in females (18.9%), and there was a much higher prevalence in all underweight categories in younger women than in men but this was reversed for older men. Conclusion: The adult population in HCMC Vietnam is in an early 'nutrition transition' with approximately equal prevalence of low and high BMI. The prevalence of overweight and obesity of Vietnamese urban adults was lower than that reported for other east and southeast Asian countries.